The present invention relates to antagonism inhibitors for herbicides which inhibit antagonism between herbicides for narrowleaf weeds and herbicides for broadleaf weeds when these herbicides are used in combination, herbicide compositions containing the antagonism inhibitor, the herbicides for narrowleaf weeds and the herbicides for broadleaf weeds, and a herbicidal method using these three agents.
From the labor-saving point of view, it is preferred to apply simultaneously herbicides for narrowleaf weeds and herbicides for broadleaf weeds in order to kill simultaneously narrowleaf weeds and broadleaf weeds which grow in the natural world, for example, farming land such as a plowland or a paddy field and non-farming land such as garden, railway bed or river bed. However, it is well known that when these are simultaneously used, there is brought about the so-called antagonism that herbicidal action or weeding action (hereinafter sometimes referred to as "herbicidal action") of one or both of these herbicides is reduced due to their interaction. It is also well known that the reduction in herbicidal action on narrowleaf weeds due to the use of the herbicides for broadleaf weeds together with those for narrowleaf weeds is conspicuous in antagonism caused by the use of both the herbicides in combination.
As one countermeasure for solving the problem, employed is a method of applying the herbicide for narrowleaf weeds and the herbicide for broadleaf weeds each alone at least twice at an interval of several days to kill the narrowleaf weeds and broadleaf weeds separately.
As another countermeasure, employed is a method of applying a mixture of these herbicides at one time wherein the application amount of the herbicide, especially the herbicide for narrowleaf weeds which compensates for the herbicidal action reduced due to the antagonism is increased.
However, the former method suffers from the problem that since the herbicides are applied at least twice, labors and amounts of adjuvants such as spreader and carriers such as water must be increased depending on increase in the number of application.
On the other hand, in the latter method, one application suffices, but amount of the herbicide, especially the herbicide for narrowleaf weeds must be increased to compensate for the herbicidal action reduced due to the antagonism. The possibility of causing the chemical injury for useful crops increases due to the increase of the application amount.
Accordingly, if chemicals which can inhibit the antagonism brought about when herbicides for narrowleaf weeds and those of broadleaf weeds are used in combination are developed, the various defects in the above-mentioned conventional application methods can be removed, weeding can be efficiently performed with less labor, without increasing the amounts of adjuvants, carriers and herbicides and with causing less chemical injure and besides, since amount of the herbicides need not be increased, the possibility of adversely affecting the environment can be reduced.
The inventors have conducted intensive research in an attempt to develop chemicals which can inhibit the antagonism brought about when herbicides for narrowleaf weeds and those of broadleaf weeds are used in combination. As a result, it has been found that this antagonism can be inhibited by using a specific hydrophilic polymeric compound containing a quaternary ammonium salt selected from many compounds. Thus, the present invention has been accomplished.